List built-in methods
Dictionary built in method
Tuple built-in method
Set built-in methods
Variable type and immutable type
The list does not produce new values after calling the built-in method
1.1 Count the number of data values in the list
l1 = ['jason', 'kevin', 'oscar', 'tony', 'jerry']
l2 = [77, 22, 55, 33, 44, 99]
# Count the number of data in the list
print(len(l1)) # 5
print(len(l2)) # 6
2. increase
2.1 Append data value to the tail append() No matter what data type is written in brackets All of them are regarded as a data value increase
# 2.1 Append data value to the tail append() No matter what data type is written in brackets Are added as a data value
res = l1.append('owen')
print(res) # None empty
print(l1) # ['jason', 'kevin', 'oscar', 'tony', 'jerry', 'owen']
s1 = '$hello$'
res1 = s1.split('$')
print(res1) # ['', 'hello', '']
print(s1) # $hello$
l1.append([1, 2, 3, 4, 5])
print(l1) # ['jason', 'kevin', 'oscar', 'tony', 'jerry', [1, 2, 3, 4, 5]]
2.2 Insert data values anywhere insert In brackets i And what data types All of them are regarded as a data subset
# Insert the data value at the desired position insert() No matter what data type is written in brackets Are inserted as a data value
l1.insert(0, [1, 2, 3])
print(l1) # [[1, 2, 3], 'jason', 'kevin', 'oscar', 'tony', 'jerry']
l2.insert(0, ' Jump the queue ') # [' Jump the queue ', [1, 2, 3], 'jason', 'kevin', 'oscar', 'tony', 'jerry']
print(l2)
2.3 Extended list
The way 1
# 2.3 Extended list
new_1 = [11, 22, 33, 44, 55]
new_2 = [1, 2, 3]
# The way 1
for i in new_1:
new_2.append(i)
print(new_2) # [1, 2, 3, 11, 22, 33, 44, 55
The way 2
# The way 2
print(new_1 + new_2) # [11, 22, 33, 44, 55, 1, 2, 3]
The way 3( Recommended ) extend
# The way 3( Recommended )
new_1.extend(new_2) # The brackets must support for The data type of the loop for loop +append()
print(new_1) # [11, 22, 33, 44, 55, 1, 2, 3]
3. Query data and modify data
# 3. Query data and modify data
print(l1) # ['jason', 'kevin', 'oscar', 'tony', 'jerry']
print(l1[0]) # jason
print(l1[1:4]) # ['kevin', 'oscar', 'tony']
l1[0] = 'jasonNM'
print(l1) # ['jasonNM', 'kevin', 'oscar', 'tony', 'jerry']
4. Delete data
4.1 Common data policy
# 4.1 Common data policy
del l1[0] # Through the index
print(l1) # ['kevin', 'oscar', 'tony', 'jerry']
4.2 Deleting by name remove
# 4.2 Delete by name
res = l1.remove('jason') # Clear data values must be filled in brackets
print(l1, res) # ['kevin', 'oscar', 'tony', 'jerry'] None
4.3 Take out the value first In the delete pop
# 4.3 Take out the data value first And then delete
res = l1.pop() # By default, the data value at the end of the list is retrieved And then delete
print(l1, res) # ['jason', 'kevin', 'oscar', 'tony'] jerry
res = l1.pop(0)
print(res, l1) # jason ['kevin', 'oscar', 'tony']
5. Look at the index values index
# 5. View the index value of the data value
print(l1.index('jason'))
6. Statistics on the occurrence of a certain data value append
# 6. Count the number of occurrences of a data value
l1.append('jason')
print(l1.count('jason')) # 2
7. Sort sort Ascending sort(reverse=True) Descending b.sort(key=a.index) duplicate removal b Press a List sort for
l2.sort() # Ascending [22, 33, 44, 55, 77, 99]
print(l2)
l2.sort(reverse=True) # Descending
print(l2) # [99, 77, 55, 44, 33, 22]
8. Flip reverse
l1.reverse() # Fall back and forth
print(l1) # ['jerry', 'tony', 'oscar', 'kevin', 'jason']
9. Comparison operations
new_1 = [99, 22]
new_2 = [11, 22, 33, 44]
print(new_1 > new_2) # True It is to compare one by one according to the position order
new_1 = ['a', 11]
new_2 = [11, 22, 33, 44]
print(new_1 > new_2) # Different data types cannot be operated directly by default
new_1 = ['a', 11] # a 97
new_2 = ['A', 22, 33, 44] # A 65
print(new_1 > new_2) # True
new_1 = [' you ', 11] # a 97
new_2 = [' I ', 22, 33, 44] # A 65
print(new_1 > new_2) # False
Dictionaries rarely involve type conversions Are directly defined and used
# Type conversion ( Understanding can ) Dictionaries rarely involve type conversions Are directly defined and used
print(dict([('name', 'jason'), ('pwd', 123)])) # {'name': 'jason', 'pwd': 123}
print(dict(name='jason', pwd=123)) # {'name': 'jason', 'pwd': 123}
1. In dictionary k:v Key value pairs are unordered
2. Value
# 2. Value operation
print(info['username']) # It is not recommended to use If the key does not exist, an error will be reported directly
print(info['xxx']) # It is not recommended to use If the key does not exist, an error will be reported directly
print(info.get('username')) # jason
print(info.get('xxx')) # None
print(info.get('username', ' The key does not have a returned value Default return None')) # jason
print(info.get('xxx', ' The key does not have a returned value Default return None')) # The key does not have a returned value Default return None
print(info.get('xxx', 123)) # 123
print(info.get('xxx')) # None
3. A dictionary of key pairs in the len
print(len(info)) # 3
4. Modifying data info
info['username'] = 'jasonNB' # If the key exists, it is modified
print(info) # {'username': 'jasonNB', 'pwd': 123, 'hobby': ['read', 'run']}
5. The new data info
# 5. The new data
info['salary'] = 6 # If the key does not exist, it is added
print(info) # {'username': 'jason', 'pwd': 123, 'hobby': ['read', 'run'], 'salary': 6}
6. Delete data
The way 1
# The way 1
del info['username']
print(info) # {'pwd': 123, 'hobby': ['read', 'run']}
The way 2
res = info.pop('username')
print(info, res) # {'pwd': 123, 'hobby': ['read', 'run']} jason
The way 3
# The way 3
info.popitem() # Random delete
print(info) # {'username': 'jason', 'pwd': 123}
7. Quick access key value Key value pair data
print(info.keys()) # Get all the dictionary's k value The result can be regarded as a list dict_keys(['username', 'pwd', 'hobby'])
print(info.values()) # Get all the dictionary's v value The result can be regarded as a list dict_values(['jason', 123, ['read', 'run']])
print(info.items()) # Get the dictionary kv Key value pair data Organize into list tuples dict_items([('username', 'jason'), ('pwd', 123), ('hobby', ['read', 'run'])])
8. Modify dictionary data If the key exists, it is modified If the key does not exist, it is added
# 8. Modify dictionary data If the key exists, it is modified If the key does not exist, it is added
info.update({'username':'jason123'})
print(info) # {'username': 'jason123', 'pwd': 123, 'hobby': ['read', 'run']}
info.update({'xxx':'jason123'})
print(info) # {'username': 'jason123', 'pwd': 123, 'hobby': ['read', 'run'], 'xxx': 'jason123'}
9. Quickly construct a dictionary Given a value, by default, all keys use a
# 9. Quickly construct a dictionary Given a value, by default, all keys use a
res = dict.fromkeys([1, 2, 3], None)
print(res) # {1: None, 2: None, 3: None}
new_dict = dict.fromkeys(['name', 'pwd', 'hobby'], []) # {'name': [], 'pwd': [], 'hobby': []}
new_dict['name'] = []
new_dict['name'].append(123)
new_dict['pwd'].append(123)
new_dict['hobby'].append('read')
print(new_dict) # {'name': [123], 'pwd': [123, 'read'], 'hobby': [123, 'read']}
res = dict.fromkeys([1, 2, 3], 234234234234234234234)
print(id(res[1])) # 2340954113104
print(id(res[2])) # 2340954113104
print(id(res[3])) # 2340954113104
10. If the key exists, get the value corresponding to the key If the key does not exist, set And return the new value set
# keyword tuple
# Type conversion Support for All data types of a loop can be converted to tuples
print(tuple(123)) # Can not be
print(tuple(123.11)) # Can not be
print(tuple('zhang')) # Sure
t1 = () # tuple
print(type(t1))
t2 = (1) # int
print(type(t2))
t3 = (11.11) # float
print(type(t3))
t4 = ('jason') # str
print(type(t4))
When there is only one data value in a tuple Commas cannot be omitted , If you omit The data type in the brackets is the data type
Suggest : Write tuples Comma plus Even if there is only one data (111, ) ('jason', )ps: In the future, you will encounter data types that can store multiple data values If there is only one data The comma also took the opportunity to add
t2 = (1,) # tuple
print(type(t2))
t3 = (11.11,) # tuple
print(type(t3))
t4 = ('jason',) # tuple
print(type(t4))
1. Count the number of tuples
t1 = (11, 22, 33, 44, 55, 66)
# 1. Count the number of data values in the tuple
print(len(t1)) # 6
2. Check and correct
# 2. Check and correct
print(t1[0]) # You can check 11
t1[0] = 222 # It can't be changed
""" The index of tuples cannot change the bound address """
t1 = (11, 22, 33, [11, 22])
t1[-1].append(33)
print(t1) # (11, 22, 33, [11, 22, 33])
set() Type conversion Support for Cyclic And the data must be immutable
1. To define an empty collection, you need to use keywords
2. Data in a collection must be of immutable type ( integer floating-point character string Tuples Boolean value )
3. duplicate removal
# duplicate removal
s1 = {1, 2, 12, 3, 2, 3, 2, 3, 2, 3, 4, 3, 4, 5, 4, 5, 4, 5, 4, 5, 4}
print(s1) # {1, 2, 3, 4, 5, 12}
l1 = ['jason', 'jason', 'tony', 'oscar', 'tony', 'oscar', 'jason']
s2 = set(l1)
l1 = list(s2)
print(l1) # ['jason', 'tony', 'oscar']
4. Simulate two people's friend collection
1. seek f1 and f2 Our mutual friends
f1 = {'jason', 'tony', 'oscar', 'jerry'}
f2 = {'kevin', 'jerry', 'jason', 'lili'}
# 1. seek f1 and f2 Our mutual friends
print(f1 & f2) # {'jason', 'jerry'}
2. seek f1/f2 Unique friends
print(f1 - f2) # {'oscar', 'tony'}
print(f2 - f1) # {'lili', 'kevin'}
3. seek f1 and f2 All friends
print(f1 | f2) # {'jason', 'kevin', 'lili', 'oscar', 'jerry', 'tony'}
4. seek f1 and f2 Their own unique friends ( Exclude common friends )
print(f1 ^ f2) # {'kevin', 'lili', 'tony', 'oscar'}
5. Superset A subset of
# 5. Superset A subset of
s1 = {1, 2, 3, 4, 5, 6, 7}
s2 = {3, 2, 1}
print(s1 > s2) # s1 Whether it is s2 A set of parent s2 Is it right? s1 Subset
print(s1 < s2)
Why do string calls to built-in methods generate new values The list calls built-in methods to change itself
1. Variable type list Value change ( Built-in methods ) The memory address can remain unchanged
# Why do string calls to built-in methods generate new values The list calls built-in methods to change itself
# 1. Variable type list Value change ( Built-in methods ) The memory address can remain unchanged
l1 = [11, 22, 33]
print(id(l1)) # 1359453669056
l1.append(44) # [11, 22, 33, 44]
print(id(l1)) # 1359453669056
2. Immutable type str int float Value change ( Built-in methods ), The memory address must have changed
# 2. Immutable type str int float Value change ( Built-in methods ), The memory address must have changed
s1 = '$hello$'
print(id(s1)) # 2807369626992#
s1 = s1.strip('$')
print(id(s1)) # 2807369039344
ccc = 666
print(id(ccc)) # 2807369267664
ccc = 990
print(id(ccc)) # 2807374985904
# 1.
# Use the list to write an employee name management system
# Input 1 Execute the function of adding user name
# Input 2 Perform the view all user names function
# Input 3 Execute the function of deleting the specified user name
# ps: Think about how to make the program loop and perform different operations according to different instructions
# Tips : Loop structure + Branching structure
# Elevation : Whether it can be replaced by dictionary or nested use of data to complete more perfect employee management rather than a simple user name ( It doesn't matter if you can write )
# 2. Remove the following list and keep the original order of data values
# eg: [1, 2, 3, 2, 1]
# After de duplication [1, 2, 3]
l1 = [2, 3, 2, 1, 2, 3, 2, 3, 4, 3, 4, 3, 2, 3, 5, 6, 5]
l2 = list(set(l1)) # Replace the list with a set, and then replace it with a list
l2.sort(key=l1.index) # Sort the de duplicated list according to the original list
print(l2)
3. There are two sets ,pythons It's registration python A collection of student names for the course ,linuxs It's registration linux A collection of student names for the course
pythons = {'jason', 'oscar', 'kevin', 'ricky', 'gangdan', 'biubiu'}
linuxs = {'kermit', 'tony', 'gangdan'}
1. Find out and sign up python Sign up again linux A collection of student names for the course
print(pythons & linuxs)
2. Find out the name set of all registered students
print(pythons | linuxs) # {'kevin', 'gangdan', 'jason', 'biubiu', 'kermit', 'tony', 'ricky', 'oscar'}
3. Only sign up python The names of the participants in the course
print(pythons - linuxs) # {'kevin', 'oscar', 'ricky', 'jason', 'biubiu'}
4. Find out the students' name set without the two courses at the same time
print(pythons ^ linuxs) # {'biubiu', 'tony', 'kermit', 'jason', 'ricky', 'oscar', 'kevin'}
Class's built-in methods ( Magic methods ): It is usually defined inside a class , With __ start __ The way to end , Are built-in methods of classes , Also called magic method . Class's built-in methods , It will automatically trigger when certain conditions are met . The built-in method is as follows : __new__: stay __ini ...
while Conditions : The sub code block executed by the loop after the condition is established Each time the subroutine of the loop body is executed, it will re judge whether the condition is true If yes, continue to execute the subcode. If not, exit break Used to end this layer cycle ### One :continu ...
# Variable type : The value has changed , however id No change , Prove that you are changing the original value instead of generating a new value , The original value is of variable type # Immutable type : The value has changed ,id Also follow change , It is proved that a new value is generated instead of changing the original value , The original value is immutable # x=10# print( ...
character string -str purpose : It is often used to record descriptive content Define methods : # You can use '','''''',"","""""" Can be used to define ...
Today is another day full of hope One .python loop 1.wuile And else Continuous use When while Not being critical 'break' In the case of active termination After the normal end of the loop body code, the else The subcode of "" ...
Have a good command of python Common data type built-in method is an internal skill that every beginner must possess . Here's how python Common types of centralized data and their methods , Open source code , The main methods are annotated in Chinese . One . integer a = 100 a.xx ...
Supplement the built-in method of string data type 1. Remove the specified characters at the beginning and end of the string to select the direction 1: s1 = '$$$jason$$$' print(s1.strip('$')) # jason print(s1.lstrip ...
Dictionary data type built-in methods ( Compulsory examination ) purpose : Save multiple values , Do not take values by index , You can use keywords to find the corresponding values Define the way :{} Internal to key:value To store multiple values , Values are separated by commas lis = ['ruixing', ...
Contents summary List built-in methods Dictionary built in method The method of converting a string into a dictionary eval() Tuple built-in method Tuple related written test questions Set built-in methods List built-in methods l1 = [2, 4, 5, 7, 3, 9, 0, 6] # l ...
1. character string Built in method operation # a = 'qqssf'#1. print(a[-1:]) # Take... By index , Forward from 0 Start , Reverse from -1 Start # print(len(a)) # Take the length # a = 'qqssf'# 2. ...
http://www.zoomfeng.com/blog/ipa-size-thin.html https://github.com/ming1016/SMCheckProject
Before, in the process of work , Yes Less, I haven't summarized my learning experience , Today, I finally have time to tidy up . Less Learn common reference documents : Less Chinese net http://lesscss.cn/ Quick start | Les ...
Before for this unique disabled Property acquisition and setting are confusing , Today's project uses , use attr Can't achieve , So many experiments have shown that : obtain disabled Properties with prop $("#basic_key") ...
dbUtils It's right JDBC Complete encapsulation of , Just import the connection pool , add to sql sentence ,dbUtils You can return result sets in various encapsulation forms . If it's Manual , stay DAO Layer using JDBC Query a statement , The following steps are required : 1 establish C ...
201421123059 http://www.cnblogs.com/deng201421123059/
poj:1258 Agri-Net Time Limit: 1000 MS Memory Limit: 10000 KB 64-bit integer IO format: %I64d , %I64u ...
Java8 lambda expression 10 Example 1. Realization Runnable Thread cases Use () -> {} Instead of anonymous classes : //Before Java 8: new Thread(new Runnab ...
Covered , Is to unload the old openssh, Clean the house and treat again ... Be careful : Please do the test well 00. View the installed on this computer openssh rpm –qa |grep openssh rpm -e openssh-s ...
Engaged in front-end has been 1 Years. , I have been worrying about the background adaptation spreading all over the screen , Because we have to adapt to different pc Monitor , So the height cannot be written dead , But write (height:100%) It doesn't work , I'm so worried ~ I don't have to write it css Implement the framework or write it yourself j ...
1 to Deskspace Set the background . stay DeskSpace Set the display background to sky box image in options ( The image effect of the software , You can also use still images , That's my own picture ) 2 Set up a background for each of the six desktops ( You can also use the same background ) Right click ...
